I've done quite a bit of boat work, and the best aluminum polish I have found is Mother's. That stuff is amazing.
That being said, when doing something big, like an entire pontoon boat, Mothers would become very expensive. When trying to find something more economical on a badly stained and oxidized pontoon boat, I decided to see what would happen if I tried using 3M Fiberglass restorer with my buffer, just like I use on fiberglass boats.
Here is the before pic, after getting the worst of the stains off with Alumabrite:
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Here is the sample spot that I did, which took maybe 15 seconds:
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It's not perfect, as there was a lot of pitting on that boat, but it looked really good, so I went on and did the rest of the boat:
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Notice the beading water. One thing I really liked is the fact that the 3M has a wax already built in, and it really did a great job, not only removing the oxidization, but in sealing and waterproofing it during the process. I did the entire boat, and it took me most of a day, but the owner was THRILLED. Now, I need to do mine, as my wife is asking me why ours doesn't look like that.
It would take a little more difficult, working between ribs and strakes, but I'm confident that it will still do a great job. Using some Alumabrite might be a good start, if you have a lot of staining, but if not, I would skip it. LDUBS, your boat is already polished, so it should be really easy on yours.
Just thought I'd share, since I saw this thread.